(1) The field of the invention comprises heat pipes for maintaining roadways and other areas free of ice, snow, and slush accumulations in colder weather by utilizing natural earth heat to melt the same, a process that involves depletion of the supply of earth heat, and, in particular, it comprises the conservation of earth heat by providing a device effective in warmer weather to augment the depleted supply of heat. (2) It is known that in summer energy is added to the earth by the ambient air and by solar radiation. Thus, a previously cooled body of earth, such as one containing up-pumping heat pipes, may be heated in this way by vertical downward conduction of heat from the surface, and it may receive even more heat by lateral conduction from contiguous surrounding earth, which itself receives heat by vertical downward conduction. But these are natural processes. So far as is known, the present invention, which aims at increasing the downward vertical conduction of heat in warmer weather, is new.